Device and method for wireless transmission

ABSTRACT

In certain aspects, a device for wireless transmission includes a transmission path, a feedback path, and a DPD control module. The transmission path includes a digital pre-distortion (DPD) conversion module configured to perform pre-distortion processing on an amplitude and a phase of a transmission signal based on a pre-distortion processing strategy. The transmission path further includes a power amplifier coupled to a downstream of the DPD conversion module and configured to amplify a power of the transmission signal. The feedback path is coupled to the transmission path at the downstream of the power amplifier and configured to generate a feedback signal. The feedback path includes a static gain compensation module configured to be activated during an initial time period of each frame to track and update a static gain for the feedback signal and configured to hold the static gain after the initial time period of each frame. The DPD control module is coupled to the feedback path and the DPD conversion module and configured to adjust the pre-distortion processing strategy based on an amplitude difference and a phase difference between the transmission signal and the feedback signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/388,306, filed on Jul. 29, 2021, entitled “DEVICE AND METHOD FORWIRELESS TRANSMISSION,” which claims the benefit of priorities toChinese Patent Application No. 202110611226.5, filed on Jun. 2, 2021,both of which are incorporated herein by reference in their entireties.

BACKGROUND

The present disclosure relates to devices for wireless transmission andprocessing methods thereof.

Power amplifiers may play an inseparable role in a wirelesscommunication system. For example, a power of a transmission signalgenerated by a modulation oscillator circuit can be relatively small andnot suitable for transmission directly. The transmission signal may needto go through a series of amplification stages including, e.g., a bufferstage, an intermediate amplification stage, and a final poweramplification stage. In this case, one or more power amplifiers may beneeded to implement the series of amplification stages. After processingthe transmission signal using the one or more power amplifiers, thetransmission signal can be fed into an antenna and transmitted to areceiver.

SUMMARY

In one aspect, a device for wireless transmission includes atransmission path, a feedback path, and a digital pre-distortion (DPD)control module. The transmission path includes a DPD conversion moduleconfigured to perform pre-distortion processing on an amplitude and aphase of a transmission signal based on a pre-distortion processingstrategy. The transmission path further includes a power amplifiercoupled to a downstream of the DPD conversion module and configured toamplify a power of the transmission signal. The feedback path is coupledto the transmission path at the downstream of the power amplifier andconfigured to generate a feedback signal. The DPD control module iscoupled to the feedback path and the DPD conversion module andconfigured to adjust the pre-distortion processing strategy based on anamplitude difference and a phase difference between the transmissionsignal and the feedback signal.

In another aspect, a method for wireless transmission is disclosed.Pre-distortion processing is performed on an amplitude and a phase of atransmission signal based on a pre-distortion processing strategy. Apower of the transmission signal is amplified. The transmission signalis transmitted through a transmitting antenna. A feedback signal isgenerated through a coupling of the transmission signal. Thepre-distortion processing strategy is adjusted based on an amplitudedifference and a phase difference between the transmission signal andthe feedback signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate aspects of the present disclosure and,together with the description, further serve to explain the principlesof the present disclosure and to enable a person skilled in thepertinent art to make and use the present disclosure.

FIG. 1A illustrates a block diagram of an exemplary device for wirelesstransmission, according to some aspects of the present disclosure.

FIG. 1B illustrates a block diagram of another exemplary device forwireless transmission, according to some aspects of the presentdisclosure.

FIG. 2 is a graphical representation illustrating a gain of a poweramplifier that changes over time, according to some aspects of thepresent disclosure.

FIG. 3A is a graphical representation illustrating a relationshipbetween an input amplitude and an output amplitude of a DPD conversionmodule, according to some aspects of the present disclosure.

FIG. 3B is a graphical representation illustrating a relationshipbetween an input amplitude and an output amplitude of a power amplifier,according to some aspects of the present disclosure.

FIG. 3C is a graphical representation illustrating a relationshipbetween an input amplitude and an output amplitude with a combinedapplication of the DPD conversion module of FIG. 3A and the poweramplifier of 3B, according to some aspects of the present disclosure.

FIG. 4A is a graphical representation illustrating a relationshipbetween a gain and an input amplitude of a DPD conversion module,according to some aspects of the present disclosure.

FIG. 4B is a graphical representation illustrating a relationshipbetween a gain and an input amplitude of a power amplifier, according tosome aspects of the present disclosure.

FIG. 4C is a graphical representation illustrating a relationshipbetween a gain and an input amplitude with a combined application of theDPD conversion module of FIG. 4A and the power amplifier of FIG. 4B,according to some aspects of the present disclosure.

FIG. 5 illustrates a flowchart of an exemplary method for wirelesstransmission, according to some aspects of the present disclosure.

FIG. 6 illustrates a flowchart of another exemplary method for wirelesstransmission, according to some aspects of the present disclosure.

The present disclosure will be described with reference to theaccompanying drawings.

DETAILED DESCRIPTION

Although specific configurations and arrangements are discussed, itshould be understood that this is done for illustrative purposes only.As such, other configurations and arrangements can be used withoutdeparting from the scope of the present disclosure. Also, the presentdisclosure can also be employed in a variety of other applications.Functional and structural features as described in the presentdisclosures can be combined, adjusted, and modified with one another andin ways not specifically depicted in the drawings, such that thesecombinations, adjustments, and modifications are within the scope of thepresent disclosure.

In general, terminology may be understood at least in part from usage incontext. For example, the term “one or more” as used herein, dependingat least in part upon context, may be used to describe any feature,structure, or characteristic in a singular sense or may be used todescribe combinations of features, structures or characteristics in aplural sense. Similarly, terms, such as “a,” “an,” or “the,” again, maybe understood to convey a singular usage or to convey a plural usage,depending at least in part upon context. In addition, the term “basedon” may be understood as not necessarily intended to convey an exclusiveset of factors and may, instead, allow for existence of additionalfactors not necessarily expressly described, again, depending at leastin part on context.

In some cases, nonlinear characteristics of a power amplifier may incurdistortion to a digital modulated signal in a transmitter of a wirelesscommunication system. This distortion may affect digital demodulation ofthe signal in a receiver and may incur in-band distortion, resulting inan increase of a bit error rate (BER) and a decrease in the datatransmission rate of the wireless communication system. The nonlinearcharacteristics of the power amplifier may also cause a spectralhyperplasia phenomenon, leading to interference with adjacent channels.Besides, with respect to a peak-to-average power ratio, orthogonalfrequency division multiplexing (OFDM), orthogonal frequency-divisionmultiple access (OFDMA), or other baseband transmission techniques underwireless standards such as WIFI5 or WIFI6 may be likely to haveoccasional peak powers. In this case, the influence of the nonlineareffect of the power amplifier on the wireless communication system maybe serious. Out-of-band spectrum spurs may occur, and an error vectormagnitude (EVM) of an entire waveform may be expanded, leading to anincreased BER.

To address one or more of the aforementioned issues, the presentdisclosure introduces a solution in which a DPD conversion module iscascaded with a power amplifier in a transmission path of a wirelesstransmitting device. The device may include the transmission pathconfigured to transmit a transmission signal, a feedback path configuredto generate a feedback signal through a coupling of the transmissionsignal, and a DPD control module configured to adaptively adjust apre-distortion processing strategy based on an amplitude difference anda phase difference between the transmission signal and the feedbacksignal. Through a combined application of the DPD conversion module andthe power amplifier in the transmission path, nonlinear characteristicsof the DPD conversion module and the power amplifier can be combined andcounteract with each other. Thus, the device can achieve high linearitywithout distortion. As a result, the BER of data transmission can bereduced, and the data transmission rate of the device can be improved.Out-of-band spectrum spurs may be reduced, and the EVM can be improved.Therefore, the transmitting performance of the device can be improved.

Consistent with certain aspects of the disclosure, the term “near realtime” may refer to a processing of data that quickly responds to anevent with a slight delay. The slight delay can be a delay ofmicroseconds (μs), milliseconds (ms), seconds or minutes, etc.,depending on various factors such as computing capabilities, availablememory space, and a sampling rate of signals, etc. For example, thepre-distortion processing described herein can be performed in near realtime with a delay of milliseconds.

FIG. 1A illustrates a block diagram of an exemplary device 100 forwireless transmission, according to some aspects of the presentdisclosure. Device 100 may include a transmission path 104, a feedbackpath 106, and a DPD control module 110. In some implementations, device100 may be a wireless transmitting device (e.g., a wireless transmitter)or a wireless transceiver. It is understood that device 100 may includeany other suitable components of a wireless transmitting device or awireless transceiver, which are not shown in the figure.

Transmission path 104 may be configured to process a transmission signaland transmit the processed transmission signal through an antenna (e.g.,a transmitting antenna 118). Transmission path 104 may include one ormore of a DPD conversion module 112, a dynamic gain compensation module113, a power amplifier 114, a coupler 116, and transmitting antenna 118.

DPD conversion module 112 may receive a transmission signal and may beconfigured to perform pre-distortion processing on an amplitude and aphase of the transmission signal based on a pre-distortion processingstrategy. DPD conversion module 112 may receive the pre-distortionprocessing strategy from DPD control module 110, which is describedbelow in more detail.

In some implementations, the pre-distortion processing strategy mayinclude an amplitude pre-distortion processing strategy used forperforming the pre-distortion processing on the amplitude of thetransmission signal. For example, the amplitude pre-distortionprocessing strategy may include a modified amplitude value for thetransmission signal, which can be determined based on a currentamplitude value of the transmission signal. The current amplitude valuecan be an amplitude value of the transmission signal at a currenttimestamp. Then, DPD conversion module 112 may change the amplitude ofthe transmission signal from the current amplitude value to the modifiedamplitude value based on the amplitude pre-distortion processingstrategy. In another example, the amplitude pre-distortion processingstrategy may include an amplitude weight for the amplitude of thetransmission signal, which can be determined based on the currentamplitude value of the transmission signal. Then, DPD conversion module112 may be configured to multiply the current amplitude value of thetransmission signal by the amplitude weight, so that the amplitude ofthe transmission signal can have the modified amplitude value.

In some implementations, the pre-distortion processing strategy may alsoinclude a phase pre-distortion processing strategy used for performingthe pre-distortion processing on the phase of the transmission signal.For example, the phase pre-distortion processing strategy may include amodified phase value for the transmission signal, which can bedetermined based on the current amplitude value of the transmissionsignal. Then, DPD conversion module 112 may be configured to change thephase of the transmission signal from a current phase value to themodified phase value based on the phase pre-distortion processingstrategy. The current phase value can be a phase value of thetransmission signal at a current timestamp. In another example, thephase pre-distortion processing strategy may include a phase weight forthe phase of the transmission signal, which can also be determined basedon the current amplitude value of the transmission signal. Then, DPDconversion module 112 may be configured to multiply the current phasevalue of the transmission signal by the phase weight, so that the phaseof the transmission signal can have the modified phase value.

Dynamic gain compensation module 113 may be configured to compensate again change caused by a temperature variation. Specifically, during atransmitting process of data frames, the temperature of circuits indevice 100 may increase gradually due to accumulated power consumptionin the transmitting process. For example, the temperature of poweramplifier 114 may increase, leading to a gain change in power amplifier114. This gain change caused by the temperature variation may bereferred to as a dynamic gain error. The dynamic gain error may betracked and compensated within the same data frame in real time or nearreal time. Otherwise, a gain of transmission path 104 may be variedgradually as the transmitting time goes by, which may cause the EVM ofthe transmission signal to become worse and worse and may have a greatimpact on the demodulation of long packets on a receiver side. In thiscase, dynamic gain compensation module 113 may be configured at adownstream of DPD conversion module 112 (or, at an upstream of poweramplifier 114) to compensate for the gain change (or the dynamic gainerror) caused by the temperature variation.

For example, dynamic gain compensation module 113 may provide a dynamicgain to the transmission signal to compensate for the gain change intransmission path 104, such that an output power of power amplifier 114can be stabilized and not varied due to the gain change. Besides,dynamic gain compensation module 113 may be connected after DPDconversion module 112, so that the dynamic gain offered by dynamic gaincompensation module 113 does not affect the performance of DPDconversion module 112. In this case, the dynamic gain compensationprovided by dynamic gain compensation module 113 and the pre-distortionprocessing provided by DPD conversion module 112 can be independent fromeach other, which may improve performances of both dynamic gaincompensation module 113 and DPD conversion module 112.

In some implementations, an initial value of the dynamic gain can beconfigured as 1 (or, 0 dB) in a first initial time period of each frame,indicating that no dynamic gain compensation is imposed on thetransmission signal in the first initial time period of each frame. Forexample, during the first initial time period of each frame, thetemperature variation is relatively small (because the transmission ofthe frame just starts), and so, the influence of the temperaturevariation on the performance of power amplifier 114 is relatively small.There is no need to perform the dynamic gain compensation. Thus, dynamicgain compensation module 113 may be configured to be activated after thefirst initial time period of each frame. For example, dynamic gaincompensation module 113 may be configured to provide a dynamic gain thatis greater than 1 (or, greater than 0 dB) after the first initial timeperiod of each frame.

In some implementations, dynamic gain compensation module 113 may beconfigured to update the dynamic gain in response to the amplitude ofthe transmission signal being in a linear region of power amplifier 114,The linear region of power amplifier 114 may be an input amplituderegion of power amplifier 114 where a gain of power amplifier 114 keepsunchanged or substantially unchanged (e.g., within a change of +5%, 10%,or another suitable value). When an amplitude value of the transmissionsignal is within the linear region of power amplifier 114, dynamic gaincompensation module 113 may track and update the dynamic gain so that aninfluence of the non-linear characteristics of power amplifier 114 onthe dynamic gain compensation can be avoided or reduced.

Power amplifier 114 may be coupled to a downstream of DPD conversionmodule 112 (or a downstream of dynamic gain compensation module 113) andconfigured to amplify the power of the transmission signal. For example,power amplifier 114 may be a radio frequency (RF) power amplifier, adirect current (DC) power amplifier, or any other suitable type of poweramplifier.

Coupler 116 may be coupled to a downstream of power amplifier 114. Forexample, coupler 116 may be coupled to an output of power amplifier 114.In some implementations, coupler 116 may be a coupler circuit includingone or more circuit elements such as a wire, a resistor, a capacitor, aninductor, etc. The transmission signal that is processed by poweramplifier 114 and outputted from power amplifier 114 may go throughcoupler 116, and may be transmitted to a receiver through transmittingantenna 118. The transmission signal may include a WIFI4 signal, a WIFI5signal, a WIFI6 signal, or any other suitable wireless signal.

Feedback path 106 may be coupled to transmission path 104 at thedownstream of the power amplifier 114 through coupler 116. Feedback path106 may be configured to generate a feedback signal through a couplingof the transmission signal at coupler 116. In some implementations,feedback path 106 may include one or more of a DC calibration module120, a static gain compensation module 122, and a synchronization module124.

DC calibration module 120 may be configured to calibrate a DC value ofthe feedback signal based on an amplitude-to-amplitude curve of poweramplifier 114 in a linear region. The amplitude-to-amplitude curve ofpower amplifier 114 may depict a relationship between an input amplitudeand an output amplitude of power amplifier 114 (e.g., as shown in FIG.3B below). In an ideal situation, when the input amplitude of poweramplifier 114 is in the linear region, the amplitude-to-amplitude curvein the linear region can be a straight line that goes through an origin.However, in practice; the output amplitude of power amplifier 114 mayhave a non-zero value when the input amplitude of power amplifier 114 iszero. This non-zero value may be incurred by a DC value of the feedbacksignal. Thus, DC calibration module 120 may calibrate or compensate theDC value of the feedback signal based on this non-zero value.

In some implementations, DC calibration module 120 may be furtherconfigured to calibrate the DC value of the feedback signal using ashort training field (STF) signal. For example, different data bits mayhave different DC components, and the DC value of the feedback signalmay be impacted by the different DC components of the different databits. However, a DC component of an STF signal can have a zero value ora known fixed value. By using the STF signal to calibrate the DC valueof the feedback signal, an influence of the DC components of thedifferent data bits on the DC value of the feedback signal can beavoided or reduced. Besides, peak amplitudes of the STF signal arerelatively small (e.g., within the linear region of power amplifier114), such that the STF signal may not be affected by the nonlinearcharacteristics of power amplifier 114.

In some implementations; a linear gain of an entire link passage ofdevice 100 (including transmission path 104 and feedback path 106) maynot be 1 (or 0 dB). The linear gain may have a value within several dBsand may be referred to as a static gain error. This static gain errormay be unchanged within a transmitting process of an entire data frameor different data frames. Static gain compensation module 122 may beconfigured to compensate for this static gain error.

Static gain compensation module 122 may be included in feedback path 106rather than transmission path 104, such that operation of static gaincompensation module 122 may not affect the gain of transmission path 104(or, the gain of power amplifier 114). Static gain compensation module122 may be activated during a second initial time period of each frame.Both the first and second initial time periods of each frame may startat the beginning of each frame. The second initial time period of eachframe may be shorter than or equal to the first initial time period ofeach frame.

Static gain compensation module 122 may be configured to track andupdate a static gain of the feedback signal during the second initialtime period of each frame and hold or keep the static gain after thesecond initial time period of each frame. For example, within aparticular initial time period of each frame (e.g., within a dozen,dozens, or hundreds of us from a start of the frame), static gaincompensation module 122 may track and update the static gain, andmeanwhile, dynamic gain compensation module 113 may not track thedynamic gain and keep the dynamic gain to be 1 (or 0 dB). After theparticular initial time period of each frame, static gain compensationmodule 122 may hold the static gain and stop updating the static gain,and dynamic gain compensation module 113 may start to track and updatethe dynamic gain. In this case, the static gain compensation and thedynamic gain compensation may not interfere with each other. Besides,within the particular initial time period of each frame, an operationtime of power amplifier 114 is relatively short and the influence of thetemperature variation on the performance of power amplifier 114 issmall. Thus, during the particular initial time period of each frame,there is no need to track and update the dynamic gain, and only thestatic gain is tracked and updated.

Synchronization module 124 may be configured to synchronize the feedbacksignal with the transmission signal. Specifically, synchronizationmodule 124 may correlate the transmission signal that is inputted intotransmission path 104 with the feedback signal that is outputted fromstatic gain compensation module 122. Then, synchronization module 124may determine a delay between the transmission signal and the feedbacksignal. Specifically, synchronization module 124 may determine the delayas a timestamp difference between a timestamp of the transmission signaland a timestamp of the feedback signal. For example, synchronizationmodule 124 may correlate the feedback signal with the transmissionsignal to obtain correlated peak values (or one or more values close tothe correlated peaks), and perform an interpolating or fitting operationon the correlated peak values (or one or more values close to thecorrelated peaks) to obtain timing information of an integer part andtiming information of a fractional part. The delay between thetransmission signal and the feedback signal may include the timinginformation of the integer part and the timing information of thefractional part. Then, synchronization module 124 may synchronize thefeedback signal with the transmission signal based on the timinginformation of the integer part and the timing information of thefractional part. For example, synchronization module 124 may perform aninterpolating operation on the feedback signal based on the timinginformation of the fractional part (e.g., as shown below using thefollowing expressions (1) and (2)) and may perform a delay operation onthe transmission signal using the timing information of the integer partthrough register delays, so that the feedback signal and thetransmission signal are synchronized with each other.

In some implementations, synchronization module 124 may include a Farrowfilter to implementation a synchronization between the feedback signaland the transmission signal. The Farrow filter may be implemented basedon the timing information of the fractional part. For example, assumingthat the timing information of the fractional part at a currenttimestamp n is 6. Coefficients of the Farrow filter can be obtainedusing the following expression (1):

$\begin{matrix}\left\{ {\begin{matrix}{{a_{1}(\theta)} = {{\alpha\theta}^{2} - {\alpha\theta}}} \\{{a_{0}(\theta)} = {{{- \alpha}\theta^{2}} + {\left( {\alpha - 1} \right)\theta} + 1}} \\{{a_{- 1}(\theta)} = {{- {\alpha\theta}^{2}} + {\left( {\alpha + 1} \right)\ \theta}}} \\{{a_{- 2}(\theta)} = {{\alpha\theta^{2}} - {\alpha\theta}}}\end{matrix}.} \right. & (1)\end{matrix}$

In the above expression (1), α denotes a parameter for determining thecoefficients a_(i) (θ) of the Farrow filter with −2≤i≤1. The feedbacksignal outputted from the Farrow filter can be obtained using thefollowing expression (2):

y _(fb)(n)=Σ_(i=−2) ¹ a _(i)(θ)x _(fb)+1+i).  (2)

In the above expression (2), x_(fb))(n+1+i) denotes the feedback signalinputted to the Farrow filter at a timestamp n+1+i. y_(fb)(n) denotesthe feedback signal outputted from the Farrow filter at the currenttimestamp n. y_(fb)(n) can be obtained as a weighted sum of x_(fb)n+1+i)using the coefficients of the Farrow filter, with −2≤i≤1. Then,synchronization module 124 may adjust the transmission signal using thetiming information of the integer part through register delays, so thatthe feedback signal y_(fb) (n) outputted from the Farrow filter issynchronized with the transmission signal adjusted using the timinginformation of the integer part.

In some implementations, the timing information of the integer part andthe timing information of the fractional part may be determined when theamplitude of the transmission signal is in a linear region of poweramplifier 114. In this case, an impact of the nonlinear characteristicsof power amplifier 114 on the performance of synchronization module 124can be reduced or eliminated, so that accuracy of the synchronizationmay be improved.

DPD control module 110 may be coupled to feedback path 106 (e.g.,coupled to synchronization module 124 of feedback path 106) and DPDconversion module 112. In some implementations, before DPD conversionmodule 112 performs the pre-distortion processing on the transmissionsignal, DPD control module 110 may be configured to determine theamplitude pre-distortion processing strategy from anamplitude-to-amplitude (AM-AM) mapping table based on the amplitude ofthe transmission signal, DPD control module 110 may also be configuredto determine the phase pre-distortion processing strategy from anamplitude-to-phase (AM-PM) mapping table based on the amplitude of thetransmission signal. The AM-AM mapping table and the AM-PM mapping tablemay be included in a lookup table (LUT) set 111. LUT set 111 may bestored in a register or a memory of device 100 and may be updated in anadaptive manner as described below in more detail.

Consistent with certain aspects of the disclosure, the AM-AM mappingtable may, include corresponding amplitude pre-distortion processingstrategies for different amplitude values. In some implementations, eachamplitude value may correspond to an AM-AM value stored in the AM-AMmapping table, and this AM-AM value can include a modified amplitudevalue or an amplitude weight corresponding to the amplitude value. Forexample, based on a current amplitude value of the transmission signal,a modified amplitude value for the transmission signal can be obtainedfrom the AM-AM mapping table. In another example, based on the currentamplitude value of the transmission signal, an amplitude weight for thetransmission signal can be obtained from the AM-AM mapping table, sothat the modified amplitude value for the transmission signal can beobtained by multiplying the current amplitude value with the amplitudeweight. Thus, the AM-AM mapping table may be used to map the currentamplitude value of the transmission signal to the modified amplitudevalue of the transmission signal.

Consistent with certain aspects of the disclosure, the AM-PM mappingtable may include corresponding phase pre-distortion processingstrategies for different amplitude values. In some implementations, eachamplitude value may correspond to an AM-PM value stored in the AM-PMmapping table, and this AM-PM value can include a modified phase valueor a phase weight corresponding to the amplitude value. For example,based on the current amplitude value of the transmission signal, amodified phase value for the transmission signal can be obtained fromthe AM-PM mapping table. In another example, based on the currentamplitude value of the transmission signal, a phase weight for thetransmission signal can be obtained from the AM-PM mapping table, sothat the modified phase value for the transmission signal can beobtained by multiplying the current phase value with the phase weight.Thus, the AM-PM mapping table may be used to map the current phase valueof the transmission signal to the modified phase value of thetransmission signal based on the current amplitude value of thetransmission signal.

In some implementations, DPD control module 110 may be configured toadjust the amplitude pre-distortion processing strategy and the phasepre-distortion processing strategy based on an amplitude difference anda phase difference between the transmission signal and the feedbacksignal. For example, DPD control module 110 may update the AM-AM mappingtable and the AM-PM mapping table based on the amplitude difference andthe phase difference between the transmission signal and the feedbacksignal. Specifically, DPD control module 110 may determine an amplitudevalue of the transmission signal at a current timestamp. DPD controlmodule 110 may determine an AM-AM value with respect to the amplitudevalue for a next timestamp based on (1) a corresponding AM-AM value withrespect to the amplitude value for the current timestamp and (2) theamplitude difference between the transmission signal and the feedbacksignal at the current timestamp. Here, the transmission signal and thefeedback signal at the current timestamp may be already synchronized andoutputted from synchronization module 124. DPD control module 110 mayalso determine an AM-PM value with respect to the amplitude value forthe next timestamp based on (1) a corresponding AM-PM value with respectto the amplitude value for the current timestamp and (2) the phasedifference between the transmission signal and the feedback signal atthe current timestamp.

For example, DPD control module 110 may determine the AM-AM value andthe AM-PM value with respect to the amplitude value for the nexttimestamp in an adaptive manner using the following expression (3):

$\begin{matrix}\left\{ {\begin{matrix}{{F_{M}^{({n + 1})}\left( a_{i} \right)} = {{F_{M}^{(n)}\left( a_{i} \right)} + {S_{M} \cdot \left( {a_{i} - a_{f}^{(n)}} \right)}}} \\{{F_{\varnothing}^{({n + 1})}\left( a_{i} \right)} = {{F_{\varnothing}^{(n)}\left( a_{i} \right)} + {S_{\varnothing} \cdot \left\lbrack \left( {V_{i} - {V_{f}^{(n)}\ {mod}2\pi}} \right. \right\rbrack}}}\end{matrix}.} \right. & (3)\end{matrix}$

In the above expression (3), a₁ and V_(i) denote the amplitude value anda phase value of the transmission signal at the current timestamp n,respectively. a_(n) ^((n)) and V_(f) ^((n)) denote an amplitude valueand a phase value of the feedback signal at the current timestamp n,respectively. The phase values V_(i) and V_(f) ^((n)) are measured inradians. F_(M) ^((n))(a_(i)) denotes the corresponding AM-AM value atthe current timestamp n with respect to the amplitude value a_(i), andF_(M) ^((n+1))(a_(i)) denotes the AM-AM value at the next timestamp n+1with respect to the amplitude value a_(i). F_(Ø) ^((n))(a₁) denotes thecorresponding AM-PM value at the current timestamp n with respect to theamplitude value a_(i), and F_(Ø) ^((n+1))(a₁) denotes the AM-PM value atthe next timestamp n+1 with respect to the amplitude value a₁. S_(M) andS_(Ø)·denote updating step sizes of the AM-AM mapping table and theAM-PM mapping table, respectively, and mod 2π denotes a modulo of 2π.

In some implementations, each of the updating step sizes S_(M) andS_(Ø)·may have a positive value close to zero, such as 0.2, 0.1, 0.01,0.001, etc. In practice, values of the updating step sizes S_(M) andS_(Ø)·can be determined based on a convergence speed of the adaptiveadjustment of the AM-AM mapping table and the AM-PM mapping table. Insome implementations, initial AM-AM values stored in the AM-AM mappingtable and initial AM-PM values stored in the AM-PM mapping table can beobtained from experimental measurements or from historical records.

In some implementations, upper and lower limits may be placed on theamplitude difference between a_(i) and a_(f) ^((n)) and the phasedifference between V_(i) and V_(f) ^((n)), respectively. For example,when the amplitude difference is calculated using a_(i)−a_(f) ^((n)) andis greater than a first amplitude difference threshold, the amplitudedifference may be determined to be equal to the first amplitudedifference threshold. When the amplitude difference is calculated usinga_(i)−a_(f) ^((n)) and is smaller than a second amplitude differencethreshold, the amplitude difference may be determined to be equal to thesecond amplitude difference threshold. The first amplitude differencethreshold can be a positive value, and the second amplitude differencethreshold can be a negative value. Similarly, when the phase differenceis calculated using V_(i)−V_(f) ^((n)) and is greater than a first phasedifference threshold, the phase difference may be determined to be equalto the first phase difference threshold. When the phase difference iscalculated using V_(i)−V_(f) ^((n)) and is smaller than a second phasedifference threshold, the phase difference may be determined to be equalto the second phase difference threshold. The first phase differencethreshold can be a positive value, and the second phase differencethreshold can be a negative value. In this case, the stability of theadaptive adjustment of the AM-AM mapping table and the AM-PM mappingtable can be improved. Thus, the performance of the adaptive adjustmentcan be improved.

In some implementations, a technique using recursive least squares(RLS), a least mean square (LMS) technique, or any other suitabletechnique can be used to implement the adaptive adjustment of the AM-AMmapping table and the AM-PM mapping table. The AM-AM mapping table andthe AM-PM mapping table may be updated using any appropriate adaptiveadjustment technique, such that DPD conversion module 112 may implementthe pre-distortion processing on the transmission signal in real time orin near real time.

In some implementations, DPD control module 110 may be configured toupdate the AM-AM mapping table and the AM-PM mapping table at an edge ofeach symbol of the transmission signal. For example, the transmissionsignal can be obtained by modulating a stream of data bits using one ormore appropriate modulation techniques such as OFDM, OFDMA, etc., andinputted into DPD conversion module 112 of transmission path 104. Thetransmission signal modulated using OFDM or OFDMA may include a streamof symbols, with each symbol including one or more subcarriers. Byupdating the AM-AM and AM-PM mapping tables at an edge of each symbol,the same AM-AM mapping table and the same AM-PM mapping table can beused to perform the pre-distortion processing for the entire symbol.This can be helpful for a demodulation process performed for the symbolon a receiver side. The transmitting performance of device 100 can beimproved.

FIG. 1B illustrates a block diagram of another exemplary device 150 forwireless transmission, according to some aspects of the presentdisclosure. In some implementations, an transmission signal and afeedback signal described herein may include a transmission basebandsignal and a feedback baseband signal, respectively. The transmissionbaseband signal may be modulated using, for example, OFDM, OFDMA,complementary code keying (CCK) that complies with the Institute ofElectrical and Electronics Engineers (IEEE) 802.11b, or any othersuitable modulation technique. Device 150 may include transmission path104, feedback path 106, and DPD control module 110. In someimplementations, device 150 may be a wireless transmitting device (e.g.,a wireless transmitter) or a wireless transceiver. It is understood thatdevice 150 may include any other suitable components of a wirelesstransmitting device or a wireless transceiver, which are not shown inthe figure.

Transmission path 104 may include one or more of a conversion module152, DPD conversion module 112, a conversion module 154, dynamic gaincompensation module 113, a digital-to-analog converter (DAC) 158, amixer 160, power amplifier 114, coupler 116, and transmitting antenna118.

In some implementations, the transmission baseband signal may include anin-phase component and a quadrature component. Conversion module 152 maybe configured to convert the in-phase component and the quadraturecomponent of the transmission baseband signal into an amplitude and aphase of the transmission baseband signal. The amplitude and the phaseof the transmission baseband signal may be inputted into DPD conversionmodule 112 and DPD control module 110.

DPD control module 110 may be configured to determine an amplitudepre-distortion processing strategy from the AM-AM mapping table based onthe amplitude of the transmission baseband signal. DPD control module110 may also be configured to determine a phase pre-distortionprocessing strategy from the AM-PM mapping table based on the amplitudeof the transmission baseband signal.

DPD conversion module 112 may be configured to perform pre-distortionprocessing on the amplitude and the phase of the transmission basebandsignal based on the amplitude pre-distortion processing strategy and thephase pre-distortion processing strategy, respectively. For example, DPDconversion module 112 may convert a current amplitude value of thetransmission baseband signal to a modified amplitude value based on theamplitude pre-distortion processing strategy. DPD conversion module 112may also convert a current phase value of the transmission basebandsignal to a modified phase value based on the phase pre-distortionprocessing strategy.

Conversion module 154 may be configured to receive the transmissionbaseband signal from DPD conversion module 112, and may convert theamplitude and the phase of the transmission baseband signal to thein-phase component and the quadrature component of the transmissionbaseband signal again.

Dynamic gain compensation module 113 may be configured to provide adynamic gain to the transmission baseband signal to compensate for again change caused by a temperature variation in transmission path 104.In some implementations, dynamic gain compensation module 113 may beconfigured to track and update the dynamic gain after a first initialtime period of each frame. In some implementations, dynamic gaincompensation module 113 may be configured to update the dynamic gain inresponse to the amplitude of the transmission baseband signal being in alinear region of power amplifier 114.

DAC 158 may be configured to convert the transmission baseband signalfrom a digital form to an analog form. Mixer 160 may be configured toperform a modulation operation on the transmission baseband signal togenerate a radio frequency (RF) transmission signal. Power amplifier 114may be configured to amplify a power of the RF transmission signal. TheRF transmission signal outputted from power amplifier 114 may go throughcoupler 116, and may be transmitted to a receiver through transmittingantenna 118.

Feedback path 106 may be configured to generate an RF feedback signalthrough a coupling of the RF transmission signal at coupler 116.Feedback path 106 may be configured to generate a feedback basebandsignal from the RF feedback signal, as described below in more detail.In some implementations, feedback path 106 may include one or more of ananalog gain adjusting module 162, a mixer 164, an analog-to-digitalconverter (ADC) 166, DC calibration module 120, a mismatch correctionmodule 170, static gain compensation module 122, synchronization module124, and a conversion module 174.

Analog gain adjusting module 162 may be configured to adjust anamplitude of the RF feedback signal. Mixer 164 may be configured toperform a demodulation operation on the RF feedback signal to generate afeedback baseband signal. ADC 166 may be configured to convert thefeedback baseband signal from an analog form to a digital form. DCcalibration module 120 may be configured to calibrate a DC value of thefeedback baseband signal based on an amplitude-to-amplitude curve ofpower amplifier 114 in a linear region. In some implementations, DCcalibration module 120 may be configured to calibrate the DC value ofthe feedback baseband signal using an STF signal.

Mismatch correction module 170 may be configured to correct a mismatchbetween an in-phase component and a quadrature component of the feedbackbaseband signal. Static gain compensation module 122 may be configuredto track and update a static gain for the feedback baseband signalduring a second initial time period of each frame and hold or keep thestatic gain after the second initial time period of each frame.Synchronization module 124 may be configured to synchronize the feedbackbaseband signal with the transmission baseband signal. Conversion module174 may be configured to convert the in-phase component and thequadrature component of the feedback baseband signal into an amplitudeand a phase of the feedback baseband signal.

DPD control module 110 may be configured to adjust the amplitudepre-distortion processing strategy and the phase pre-distortionprocessing strategy based on an amplitude difference and a phasedifference between the transmission baseband signal and the feedbackbaseband signal. For example, DPD control module 110 may be configuredto update the AM-AM mapping table and the AM-PM mapping table based onan amplitude difference and a phase difference between the transmissionbaseband signal and the feedback baseband signal.

Specifically, DPD control module 110 may determine an amplitude value ofthe transmission baseband signal at a current timestamp. DPD controlmodule 110 may determine an AM-AM value with respect to the amplitudevalue for a next timestamp based on (1) a corresponding AM-AM value withrespect to the amplitude value for the current timestamp and (2) theamplitude difference between the transmission baseband signal and thefeedback baseband signal at the current timestamp. DPD control module110 may also determine an AM-PM value with respect to the amplitudevalue for the next timestamp based on (1) a corresponding AM-PM valuewith respect to the amplitude value for the current timestamp and (2)the phase difference between the transmission baseband signal and thefeedback baseband signal at the current timestamp. For example, DPDcontrol module 110 may be configured to determine the AM-AM value andthe AM-PM value with respect to the amplitude value for the nexttimestamp in an adaptive manner using the above expression (3).

Consistent with the description of FIGS. 1A-1B, through a combinedapplication of DPD conversion module 112 and power amplifier 114 intransmission path 104, nonlinear characteristics of DPD conversionmodule 112 and power amplifier 114 can be combined and counteract witheach other. Thus, device 100 or 150 can achieve high linearity withoutdistortion. As a result, the BER of data transmission can be reduced,and a data transmission rate of device 100 or 150 can be improved.Furthermore, out-of-band spectrum spurs may be reduced, and the EVM canbe improved.

Consistent with the description of FIGS. 1A-1B, device 100 or 150 mayinclude one or more processors, one or more programmable logic devices(e.g., field programmable gate arrays (FPGAs)), and/or one or morecircuits (e.g., application specific integrated circuits (ASICs)) forproviding functions disclosed herein. For example, device 100 or 150 mayinclude a system-on-chip (SoC) on a circuit board. The one or moreprocessors may include a microprocessor unit (MPU), a microcontrollerunit (MCU), a digital signal processor (DSP), or any other suitable typeof processor.

Functions of various components or modules of device 100 or 150 may beimplemented using hardware, software, or a combination thereof. In someimplementations, the components or modules of device 100 or 150 may behardware units (e.g., portions of an integrated circuit) configured toprovide the functions described herein. For example, transmittingantenna 118 may be placed outside an integrated circuit (IC) and locatedon a printed circuit board (PCB), while the other components or modulesof device 100 or 150 may be integrated into the IC on the PCB. In someimplementations, the components or modules of device 100 or 150 may besoftware units (e.g., code or routines) implemented by a processorthrough executing at least part of a program. The program may be storedon a non-transitory computer-readable medium, such as a memory or astorage, and when executed by the processor, it may perform thefunctions described herein. In some implementations, the components ormodules of device 100 or 150 may be implemented using a combination ofhardware units and software units.

FIG. 2 is a graphical representation 200 illustrating a gain of a poweramplifier (e.g., power amplifier 114) that changes over time, accordingto some aspects of the present disclosure. For example, as more and moredata bits in a frame are transmitted, the temperature of power amplifier114 may increase, causing the gain of power amplifier 114 to decrease,as shown in FIG. 2. Thus, dynamic gain compensation module 113 may beconfigured to compensate this gain change of power amplifier 114 asdescribed above, and the similar description will not be repeated here.

FIG. 3A is a graphical representation 300 illustrating a relationshipbetween an input amplitude and an output amplitude of a DPD conversionmodule (e.g., DPD conversion module 112), according to some aspects ofthe present disclosure. When the input amplitude of DPD conversionmodule 112 is relatively small (e.g., not greater than a firstthreshold), the output amplitude of DPD conversion module 112 has alinear relationship with the input amplitude. However, when the inputamplitude of DPD conversion module 112 becomes large (e.g., greater thanthe first threshold), the output amplitude of DPD conversion module 112grows exponentially with respect to the input amplitude.

FIG. 3B is a graphical representation 310 illustrating a relationshipbetween an input amplitude and an output amplitude of a power amplifier(e.g., power amplifier 114), according to some aspects of the presentdisclosure. When the input amplitude of power amplifier 114 isrelatively small (e.g., not greater than a second threshold), the outputamplitude of power amplifier 114 has a linear relationship with theinput amplitude. However, when the input amplitude of power amplifier114 becomes large (e.g., greater than the second threshold), the outputamplitude of power amplifier 114 approaches an upper limit gradually.

FIG. 3C is a graphical representation 320 illustrating a relationshipbetween an input amplitude and an output amplitude with a combinedapplication of DPD conversion module 112 of FIG. 3A and power amplifier114 of FIG. 3B, according to some aspects of the present disclosure.FIG. 3C illustrates that the input amplitude to the combined applicationof DPD conversion module 112 and power amplifier 114 may have a linearrelationship with the output amplitude from the combined application ofDPD conversion module 112 and power amplifier 114. The nonlinearcharacteristics of DPD conversion module 112 and power amplifier 114 maycounteract each other.

FIG. 4A is a graphical representation 400 illustrating a relationshipbetween a gain and an input amplitude of a DPD conversion module (e.g.,DPD conversion module 112), according to some aspects of the presentdisclosure. When the input amplitude of DPD conversion module 112 isrelatively small (e.g., not greater than a third threshold), the gain ofDPD conversion module 112 is almost constant. However, when the inputamplitude of DPD conversion module 112 becomes large (e.g., greater thanthe third threshold), the gain of DPD conversion module 112 increaseswith respect to an increase of the input amplitude.

FIG. 4B is a graphical representation 410 illustrating a relationshipbetween a gain and an input amplitude of a power amplifier (e.g., poweramplifier 114), according to some aspects of the present disclosure.When the input amplitude of power amplifier 114 is relatively small(e.g., not greater than a fourth threshold), the gain of power amplifier114 is almost constant. However, when the input amplitude of poweramplifier 114 becomes large (e.g., greater than the fourth threshold),the gain of power amplifier 114 decreases with respect to an increase ofthe input amplitude.

FIG. 4C is a graphical representation 420 illustrating a relationshipbetween a gain and an input amplitude with a combined application of DPDconversion module 112 of FIG. 4A and power amplifier 114 of FIG. 4B,according to some aspects of the present disclosure. FIG. 4C illustratesthat the gain from the combined application of DPD conversion module 112and power amplifier 114 may keep constant with respect to the inputamplitude to the combined application of DPD conversion module 112 andpower amplifier 114. Thus, the nonlinear characteristics of DPDconversion module 112 and power amplifier 114 may counteract each other.

FIG. 5 illustrates a flowchart of an exemplary method 500 for wirelesstransmission, according to some aspects of the present disclosure.Method 500 may be implemented by device 100 or 150, It is understoodthat the operations shown in method 500 may not be exhaustive and thatother operations can be performed as well before, after, or between anyof the illustrated operations. Further, some of the operations may beperformed simultaneously, or in a different order than shown in FIG. 5 .

Referring to FIG. 5 , method 500 starts at operation 502, in whichpre-distortion processing is performed on an amplitude and a phase of atransmission signal based on a pre-distortion processing strategy. Forexample, DPD control module 110 may determine an amplitudepre-distortion processing strategy from an AM-AM mapping table based onan amplitude of the transmission signal. DPD control module 110 may alsodetermine a phase pre-distortion processing strategy from an AM-PMmapping table based on the amplitude of the transmission signal. DPDconversion module 112 may perform the pre-distortion processing on theamplitude of the transmission signal based on the amplitudepre-distortion processing strategy. DPD conversion module 112 may alsoperform the pre-distortion processing on the phase of the transmissionsignal based on the phase pre-distortion processing strategy.

In some implementations, a gain change of the transmission signal causedby a temperature variation may be compensated. For example, a dynamicgain may be tracked and updated after a first initial time period ofeach frame and provided to the transmission signal.

Method 500 proceeds to operation 504, as illustrated in FIG. 5 , inwhich a power of the transmission signal is amplified. For example,power amplifier 114 may amplify the power of the transmission signal.

Method 500 proceeds to operation 506, as illustrated in FIG. 5 , inwhich the transmission signal is transmitted through transmittingantenna 118.

Method 500 proceeds to operation 508, as illustrated in FIG. 5 , inwhich a feedback signal is generated through a coupling of thetransmission signal. For example, feedback path 106 generates a feedbacksignal from the coupling of the transmission signal through coupler 116.

In some implementations, a DC value of the feedback signal may becalibrated based on an amplitude-to-amplitude curve of power amplifier114 in a linear region. In some implementations, a static gain of thefeedback signal may be tracked and updated during a second initial timeperiod of each frame. In some implementations, the DC value of thefeedback signal may be calibrated using an STF signal. In someimplementations, the feedback signal may be synchronized with thetransmission signal.

Method 500 proceeds to operation 510, as illustrated in FIG. 5 , inwhich the pre-distortion processing strategy is adjusted based on anamplitude difference and a phase difference between the transmissionsignal and the feedback signal.

In some implementations, the AM-AM mapping table and the AM-PM mappingtable may be updated based on the amplitude difference and the phasedifference between the transmission signal and the feedback signal.Specifically, an amplitude value of the transmission signal at a currenttimestamp can be determined. An AM-AM value with respect to theamplitude value for a next timestamp can be determined based on acorresponding AM-AM with respect to the amplitude value for the currenttimestamp and the amplitude difference between the transmission signaland the feedback signal at the current timestamp. An AM-PM value withrespect to the amplitude value for the next timestamp can be determinedbased on a corresponding AM-PM value with respect to the amplitude valuefor the current timestamp and the phase difference between thetransmission signal and the feedback signal at the current timestamp.For example, the AM-AM value and the AM-PM value for the next timestampcan be determined in an adaptive manner using the above expression (3).

In some implementations, the AM-AM mapping table and the AM-PM mappingtable may be updated at an edge of each symbol of the transmissionsignal.

FIG. 6 illustrates a flowchart of another exemplary method 600 forwireless transmission, according to some aspects of the presentdisclosure. Method 600 may be implemented by device 100 or 150. It isunderstood that the operations shown in method 600 may not be exhaustiveand that other operations can be performed as well before, after, orbetween any of the illustrated operations. Further, some of theoperations may be performed simultaneously, or in a different order thanshown in FIG. 6 .

Referring to FIG. 6 , method 600 starts at operation 602, in which atransmission baseband signal may be received by transmission path 104.

Method 600 proceeds to operation 604, as illustrated in FIG. 6 , inwhich an amplitude and a phase of the transmission baseband signal aredetermined.

Method 600 proceeds to operation 606, as illustrated in FIG. 6 , inwhich pre-distortion processing is performed on the amplitude and thephase of the transmission baseband signal based on an amplitudepre-distortion processing strategy and a phase pre-distortion processingstrategy, respectively.

Method 600 proceeds to operation 608, as illustrated in FIG. 6 , inwhich subsequent processing is performed on the transmission basebandsignal to obtain an RF transmission signal. For example, the subsequentprocessing may include one or more operations performed by conversionmodule 154, dynamic gain compensation module 113, DAC 158, mixer 160,power amplifier 114, and coupler 116 disclosed herein.

Method 600 proceeds to operation 610, as illustrated in FIG. 6 , inwhich the RF transmission signal is transmitted through transmittingantenna 118.

Method 600 proceeds to operation 612, as illustrated in FIG. 6 , inwhich a feedback baseband signal is generated by feedback path 106. Forexample, an RF feedback signal may be generated through a coupling ofthe RF transmission signal. The RF feedback signal may be transformedinto the feedback baseband signal. A DC value of the feedback basebandsignal may, be calibrated by DC calibration module 120. Static gaincompensation module 122 may perform a static gain compensation on thefeedback baseband signal.

Method 600 proceeds to operation 614, as illustrated in FIG. 6 , inwhich the feedback baseband signal is synchronized with the transmissionbaseband signal.

Method 600 proceeds to operation 616, as illustrated in FIG. 6 , inwhich the amplitude pre-distortion processing strategy and the phasepre-distortion processing strategy are adjusted based on an amplitudedifference and a phase difference between the transmission basebandsignal and the feedback baseband signal, respectively.

According to one aspect of the present disclosure, a device for wirelesstransmission includes a transmission path, a feedback path, and a DPDcontrol module. The transmission path includes a DPD conversion moduleconfigured to perform pre-distortion processing on an amplitude and aphase of a transmission signal based on a pre-distortion processingstrategy. The transmission path further includes a power amplifiercoupled to a downstream of the DPD conversion module and configured toamplify a power of the transmission signal. The feedback path is coupledto the transmission path at the downstream of the power amplifier andconfigured to generate a feedback signal. The DPD control module iscoupled to the feedback path and the DPD conversion module andconfigured to adjust the pre-distortion processing strategy based on anamplitude difference and a phase difference between the transmissionsignal and the feedback signal.

In some implementations, the pre-distortion processing strategy includesan amplitude pre-distortion processing strategy for performing thepre-distortion processing on the amplitude of the transmission signal.The pre-distortion processing strategy further includes a phasepre-distortion processing strategy for performing the pre-distortionprocessing on the phase of the transmission signal.

In some implementations, the DPD control module is configured to:determine the amplitude pre-distortion processing strategy from an AM-AMmapping table based on the amplitude of the transmission signal; anddetermine the phase pre-distortion processing strategy from an AM-PMmapping table based on the amplitude of the transmission signal.

In some implementations, to adjust the pre-distortion processingstrategy, the DPD control module is further configured to update theAM-AM mapping table and the AM-PM mapping table based on the amplitudedifference and the phase difference between the transmission signal andthe feedback signal.

In some implementations, to update the AM-AM mapping table and theAM-PMI mapping table, the DPD control module is further configured to:determine an amplitude value of the transmission signal at a currenttimestamp; determine an AM-AM value with respect to the amplitude valuefor a next timestamp based on a corresponding AM-AM value with respectto the amplitude value for the current timestamp and the amplitudedifference between the transmission signal and the feedback signal atthe current timestamp; and determine an AM-PM value with respect to theamplitude value for the next timestamp based on a corresponding AM-PMvalue with respect to the amplitude value for the current timestamp andthe phase difference between the transmission signal and the feedbacksignal at the current timestamp.

In some implementations, the DPD control module may be configured todetermine the AM-AM value and the AM-PM value with respect to theamplitude value for the next timestamp in an adaptive manner as follows:

$\left\{ {\begin{matrix}{{F_{M}^{({n + 1})}\left( a_{i} \right)} = {{F_{M}^{(n)}\left( a_{i} \right)} + {S_{M} \cdot \left( {a_{i} - a_{f}^{(n)}} \right)}}} \\{{F_{\varnothing}^{({n + 1})}\left( a_{i} \right)} = {{F_{\varnothing}^{(n)}\left( a_{i} \right)} + {S_{\varnothing} \cdot \left\lbrack \left( {V_{i} - {V_{f}^{(n)}\ {mod}2\pi}} \right. \right\rbrack}}}\end{matrix},} \right.$

where a₁ and V_(i) denote the amplitude value and a phase value of thetransmission signal at the current timestamp n, respectively. a_(n)^((n)) and V_(f) ^((n)) denote an amplitude value and a phase value ofthe feedback signal at the current timestamp n, respectively. F_(M)^((n))(a_(i)) denotes the corresponding AM-AM value with respect to theamplitude value a_(i) for the current timestamp n, and F_(M)^((n+1))(a_(i)) denotes the AM-AM value with respect to the amplitudevalue a_(i) for the next timestamp n+1. F_(Ø) ^((n))(a₁) denotes thecorresponding AM-PM value with respect to the amplitude value a_(i) forthe current timestamp n, and F_(Ø) ^((n+1))(a₁) denotes the AM-PM valuewith respect to the amplitude value a₁ for the next timestamp n+1. S_(M)and S_(Ø)·denote updating step sizes of the AM-AM mapping table and theAM-PM mapping table, respectively, and mod 2π denotes a modulo of 2π.

In some implementations, the DPD control module is configured to updatethe AM-AM mapping table and the AM-PM mapping table at an edge of eachsymbol of the transmission signal.

In some implementations, the transmission path further includes adynamic gain compensation module configured at a downstream of the DPDconversion module to compensate a gain change caused by a temperaturevariation.

In some implementations, the dynamic gain compensation module isconfigured to be activated after a first initial time period of eachframe to track and update a dynamic gain for the transmission signal.

In some implementations, the feedback path includes a static gaincompensation module configured to be activated during a second initialtime period of each frame to track and update a static gain for thefeedback signal and configured to hold the static gain after the secondinitial time period of each frame.

In some implementations, the feedback path includes a DC calibrationmodule configured to calibrate a DC value of the feedback signal basedon an amplitude-to-amplitude curve of the power amplifier in a linearregion.

In some implementations, the DC calibration module is further configuredto calibrate the DC value of the feedback signal using an STF signal.

In some implementations, the feedback path includes a synchronizationmodule configured to synchronize the feedback signal with thetransmission signal.

In some implementations, the synchronization module includes a Farrowfilter implemented based on timing information of an integer part andtiming information of a fractional part. The timing information of theinteger part and the timing information of the fractional part aredetermined in response to the amplitude of the transmission signal beingin a linear region of the power amplifier.

In some implementations, the transmission signal includes a transmissionbaseband signal, and the feedback signal includes a feedback basebandsignal.

In some implementations, the transmission signal includes a WIFI4signal, a WIFI5 signal, or a WIFI6 signal.

According to another aspect of the present disclosure, a method forwireless transmission is disclosed. Pre-distortion processing isperformed on an amplitude and a phase of a transmission signal based ona pre-distortion processing strategy. A power of the transmission signalis amplified. The transmission signal is transmitted through atransmitting antenna. A feedback signal is generated through a couplingof the transmission signal. The pre-distortion processing strategy isadjusted based on an amplitude difference and a phase difference betweenthe transmission signal and the feedback signal.

In some implementations, the pre-distortion processing strategy includesan amplitude pre-distortion processing strategy for performing thepre-distortion processing on the amplitude of the transmission signal.The pre-distortion processing strategy further includes a phasepre-distortion processing strategy for performing the pre-distortionprocessing on the phase of the transmission signal.

In some implementations, the amplitude pre-distortion processingstrategy is determined from an AM-AM mapping table based on theamplitude of the transmission signal. The phase pre-distortionprocessing strategy is determined from an AM-PM mapping table based onthe amplitude of the transmission signal.

In some implementations, adjusting the pre-distortion processingstrategy includes updating the AM-AM mapping table and the AM-PM mappingtable based on the amplitude difference and the phase difference betweenthe transmission signal and the feedback signal.

The foregoing description of the specific implementations can be readilymodified and/or adapted for various applications. Therefore, suchadaptations and modifications are intended to be within the meaning andrange of equivalents of the disclosed implementations, based on theteaching and guidance presented herein.

The breadth and scope of the present disclosure should not be limited byany of the above-described exemplary implementations, but should bedefined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A device for wireless transmission, comprising: atransmission path comprising: a digital pre-distortion (DPD) conversionmodule configured to perform pre-distortion processing on an amplitudeand a phase of a transmission signal based on a pre-distortionprocessing strategy; and a power amplifier coupled to a downstream ofthe DPD conversion module and configured to amplify a power of thetransmission signal; a feedback path coupled to the transmission path atthe downstream of the power amplifier and configured to generate afeedback signal, wherein the feedback path comprises a static gaincompensation module configured to be activated during an initial timeperiod of each frame to track and update a static gain for the feedbacksignal and configured to hold the static gain after the initial timeperiod of each frame; and a DPD control module coupled to the feedbackpath and the DPD conversion module, and configured to adjust thepre-distortion processing strategy based on an amplitude difference anda phase difference between the transmission signal and the feedbacksignal.
 2. The device of claim 1, wherein the pre-distortion processingstrategy comprises: an amplitude pre-distortion processing strategy forperforming the pre-distortion processing on the amplitude of thetransmission signal; and a phase pre-distortion processing strategy forperforming the pre-distortion processing on the phase of thetransmission signal.
 3. The device of claim 2, wherein the DPD controlmodule is configured to: determine the amplitude pre-distortionprocessing strategy from an amplitude-to-amplitude (AM-AM) mapping tablebased on the amplitude of the transmission signal; and determine thephase pre-distortion processing strategy from an amplitude-to-phase(AM-PM) mapping table based on the amplitude of the transmission signal.4. The device of claim 3, wherein to adjust the pre-distortionprocessing strategy, the DPD control module is further configured toupdate the AM-AM mapping table and the AM-PM mapping table based on theamplitude difference and the phase difference between the transmissionsignal and the feedback signal.
 5. The device of claim 4, wherein toupdate the AM-AM mapping table and the AM-PM mapping table, the DPDcontrol module is further configured to: determine an amplitude value ofthe transmission signal at a current timestamp; determine an AM-AM valuewith respect to the amplitude value for a next timestamp based on acorresponding AM-AM value with respect to the amplitude value for thecurrent timestamp and the amplitude difference between the transmissionsignal and the feedback signal at the current timestamp; and determinean AM-PM value with respect to the amplitude value for the nexttimestamp based on a corresponding AM-PM value with respect to theamplitude value for the current timestamp and the phase differencebetween the transmission signal and the feedback signal at the currenttimestamp.
 6. The device of claim 5, wherein the DPD control module isconfigured to determine the AM-AM value and the AM-PM value for the nexttimestamp in an adaptive manner as follows: $\left\{ {\begin{matrix}{{F_{M}^{({n + 1})}\left( a_{i} \right)} = {{F_{M}^{(n)}\left( a_{i} \right)} + {S_{M} \cdot \left( {a_{i} - a_{f}^{(n)}} \right)}}} \\{{F_{\varnothing}^{({n + 1})}\left( a_{i} \right)} = {{F_{\varnothing}^{(n)}\left( a_{i} \right)} + {S_{\varnothing} \cdot \left\lbrack \left( {V_{i} - {V_{f}^{(n)}\ {mod}2\pi}} \right. \right\rbrack}}}\end{matrix},} \right.$ wherein a_(i) and V_(i) denote the amplitudevalue and a phase value of the transmission signal at the currenttimestamp n, respectively; a_(f) ^((n)) and V_(f) ^((n)) denote anamplitude value and a phase value of the feedback signal at the currenttimestamp n, respectively; F_(M) ^((n))(a_(i)) denotes the correspondingAM-AM value with respect to the amplitude value a_(i) for the currenttimestamp n, and F_(M) ^((n+1))(a_(i)) denotes the AM-AM value withrespect to the amplitude value a_(i) for the next timestamp n+1; F_(Ø)^((n)) (a_(i)) denotes the corresponding AM-PM value with respect to theamplitude value a_(i) for the current timestamp n, and F_(Ø)^((n+1))(a_(i)) denotes the AM-PM value with respect to the amplitudevalue a_(i) for the next timestamp n+1; S_(M) and S_(Ø)·denote updatingstep sizes of the AM-AM mapping table and the AM-PM mapping table,respectively; and mod 2π denotes a modulo of 2π.
 7. The device of claim4, wherein the DPD control module is configured to update the AM-AMmapping table and the AM-PM mapping table at an edge of each symbol ofthe transmission signal.
 8. The device of claim 1, wherein thetransmission path further comprises a dynamic gain compensation moduleconfigured at a downstream of the DPD conversion module to compensate again change caused by a temperature variation.
 9. The device of claim 8,wherein the dynamic gain compensation module is configured to beactivated after another initial time period of each frame to track andupdate a dynamic gain for the transmission signal.
 10. The device ofclaim 1, wherein the feedback path comprises a direct current (DC)calibration module configured to calibrate a DC value of the feedbacksignal based on an amplitude-to-amplitude curve of the power amplifierin a linear region.
 11. The device of claim 10, wherein the DCcalibration module is further configured to calibrate the DC value ofthe feedback signal using a short training field (STF) signal.
 12. Thedevice of claim 1, wherein the feedback path comprises a synchronizationmodule configured to synchronize the feedback signal with thetransmission signal.
 13. The device of claim 12, wherein thesynchronization module comprises a Farrow filter implemented based oninformation of an integer part and timing information of a fractionalpart; and the timing information of the integer part and the timinginformation of the fractional part are determined in response to theamplitude of the transmission signal being in a linear region of thepower amplifier.
 14. The device of claim 1, wherein the transmissionsignal comprises a transmission baseband signal, and the feedback signalcomprises a feedback baseband signal.
 15. The device of claim 1; whereinthe transmission signal comprises a WIFI4 signal, a WIFI5 signal, or aWIFI6 signal.
 16. A method for wireless transmission, comprising:performing pre-distortion processing on an amplitude and a phase of atransmission signal based on a pre-distortion processing strategy;amplifying a power of the transmission signal; transmitting thetransmission signal through a transmitting antenna; generating afeedback signal through a coupling of the transmission signal, wherein astatic gain for the feedback signal is tracked and updated during aninitial time period of each frame and is held after the initial timeperiod of each frame; and adjusting the pre-distortion processingstrategy based on an amplitude difference and a phase difference betweenthe transmission signal and the feedback signal.
 17. The method of claim16, wherein the pre-distortion processing strategy comprises: anamplitude pre-distortion processing strategy for performing thepre-distortion processing on the amplitude of the transmission signal;and a phase pre-distortion processing strategy for performing thepre-distortion processing on the phase of the transmission signal. 18.The method of claim 17, further comprising: determining the amplitudepre-distortion processing strategy from an amplitude-to-amplitude(AM-AM) mapping table based on the amplitude of the transmission signal;and determining the phase pre-distortion processing strategy from anamplitude-to-phase (AM-PM) mapping table based on the amplitude of thetransmission signal.
 19. The method of claim 18, wherein adjusting thepre-distortion processing strategy comprises updating the AM-AM mappingtable and the AM-PM mapping table based on the amplitude difference andthe phase difference between the transmission signal and the feedbacksignal.
 20. The method of claim 19, wherein updating the AM-AM mappingtable and the AM-PM mapping table comprises: determining an amplitudevalue of the transmission signal at a current timestamp; determining anAM-AM value with respect to the amplitude value for a next timestampbased on a corresponding AM-AM value with respect to the amplitude valuefor the current timestamp and the amplitude difference between thetransmission signal and the feedback signal at the current timestamp;and determining an AM-PM value with respect to the amplitude value forthe next timestamp based on a corresponding AM-PM value with respect tothe amplitude value for the current timestamp and the phase differencebetween the transmission signal and the feedback signal at the currenttimestamp.